The Entanglement and Relaxation of Liquid Crystal Shaped Granular Media

Theresa Albon

2013

The intention of this research was to analyze properties of microscopic liquid crystal molecules. Since working with microscopic molecules can be difficult a macroscopic model was made out of wires shaped like H, U, V, and rod shaped liquid crystal molecules. An experiment was done to analyze the collapse or relaxation of entangled wires of various shapes under sinusoidal relaxation accelerations. A MATLAB program was made to find the centroid and total pixel area of the entangled pile in every other frame of the video during the collapse. The centroid data was fitted with double exponential fits, which yielded two characteristic times for the collapse process. From this analysis, we concluded that the V and rod shaped wires behaved similarly, they did not display entanglement and would easily collapse. The U-shaped wires displayed the greatest amount of entanglement and would remain entangled together the longest out of all of the wires analyzed. A computer simulation was written to recreate the experiment. Only rods were analyzed and they varied in number: 50, 100, and 200. In addition to analyzing the relaxation height, the decrease in height due to entanglement from when the rods were first placed in an enclosure and accelerated, was analyzed. Only the data runs with 100 rods displayed any decrease in height, due to their alignment within the enclosure. The decrease in height during the relaxations also were fitted with a double exponential fit. The V and rod wire shapes were easily untangled during the relaxation portion of the experimental research, this suggested that V and rod shaped liquid crystals have a low elastic energy. The rod wires would align parallel to one another in the experiment and computer simulation and form a layer of rods, this suggests that the rod shaped liquid crystal molecules have the greatest orientational and positional order. The ability to relax when the wires were free of their enclosure and subjected to an acceleration compares with a liquid crystal's molecular viscosity. Since the U-shaped wires displayed the greatest entanglement, this research suggests that they have the highest viscosity, while the rod shaped liquid crystal molecules would have the lowest viscosity.